Brother HL-4000CN Service Manual page 290

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Fig.5-23
Condition:
Print is wholly white.
Initial check:
Parts of different specifications, improper installation, damage, deformation, dirt, foreign
substance attached, etc.
Major parts to be checked:
Print head cartridge ASSY, Fuser ASSY, Transfer roll cartridge ASSY, Scanner ASSY,
MCU and HVPS PWB, Toner cartridge
Item Check
Toner empty
1
Check if the toner cartridge is full with toner.
Laser beam path interrupted
Check the laser beam path between scanner ASSY
2
and the drum in print head cartridge ASSY for
evidence of dirt or foreign substances.
Faulty scanner ASSY
3 Is the image quality improved if scanner ASSY is
replaced?
Faulty charging or developing
4 Is the image quality improved if print head cartridge
ASSY is replaced?
Faulty transfer
5 Is the image quality improved if transfer roll
cartridge is replaced?
Faulty MCU and HVPS PWB
6 Is the image quality improved if MCU and HVPS PW
is replaced?
V-80
Remedy
Replace the toner
cartridge
Clean dirt or foreign
substances
Replace the scanner
ASSY
Replace the print head
cartridge ASSY
Replace the transfer roll
cartridge ASSY
Replace the MCU and
HVPS PWB